The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information available to management and research user groups. This ongoing project began in 1988. A total of 38 subsurface recording thermographs have been deployed in the Florida Keys National Marine Sanctuary (FKNMS) and at other selected locations on the Florida Reef Tract and associated hydrologic ecosystems. These instruments have been programmed to record at 2 hour intervals and are placed in permanent housings attached to suitable substrate. Data retrieval, servicing and reprogramming for continuous deployment have occurred, on average, annually. Initially, the collected data are made available to FKNMS Managers and others who monitor and assess environmental conditions that influence FKNMS areas of the Florida Reef Tract. An archival copy of these data is maintained and available from the U.S. NODC.